High-capacity radio systems require deployment of small cells, where a great number of antennas cover a given area. Whereas outdoor cell diameters in 2nd/3rd generation radio networks are in the area of 1-10 km, Long Term Evolution (LTE)/WiFi indoor cell diameters can be as low as 5-10 meters.
Traditionally, advanced network planning and optimization tools are used to determine suitable geographic radio base station (RBS)/antenna deployment locations and to tune network parameters such as sector azimuth, down tilt, power, etc. for optimum coverage, maximum data rate, and minimum cell interference. For ultra high-density small cell architectures—especially indoors—those tools are limited due to the potentially large scale of the network and plug-and-play (i.e. self-install) requirements. Remote radio heads are required to support low-cost installation and operation of high-density small-cell radio networks.
A remote radio head is an inexpensive, low-power radio unit which is remote from and connected to the “ordinary” base transceiver station (BTS) and is used to extend the coverage of the BTS (or NodeB/eNodeB) in indoor deployments such as enterprise offices, multi-tenant high rise buildings, shopping malls, airports, metros, tunnels, arenas, etc. The remote radio head generally connects to the BTS/NodeB/eNodeB via existing copper cabling such as Ethernet cable plants or coax cables. In main-remote deployments, several radio heads connect to a multi-port remote radio unit (RRU) which backhauls the baseband-signals to a base-band digital unit via common public radio interface (CPRI) physically transported over fiber links.
In existing small cell networks, pico or femto RBSs are fixedly installed to create small cell deployments. Typically, the base station functionality is integrated in small nodes and IP traffic is backhauled to the core network by the usage of small-formfactor (SFP) pluggables supporting different media types such as fiber/copper of different reach. Advantageously, if e.g. bandwidth requirements increase, or of different types of traffic are required, one or more SFP modules can be plugged in making the small-cell RBS highly scalable. Power is provided to the small-cell RBS from local grid.
Radio heads are targeted to be powered remotely from the RBS with which the radio head communicates via analog radio signal transmission on the copper cable. The remote power transfer is facilitated from power sourcing equipment (PSE) inside the RBS over Ethernet cabling towards a powered device (PD) at the radio head using Power-over-Ethernet (PoE). This allows deploying radio heads freely without local grid power.
Further, all-band radio heads are expensive as compared to using different radio heads for e.g. different radio bands, transmit power, radio standards, etc.